The invention relates to apparatus and methods for handling a substrate.
Apparatus and methods for handling substrates are used in a variety of applications. For example, in semiconductor processing applications, a substrate may be handled by an automated transfer mechanism, such as a transfer robot, which transfers substrates into and out of one or more semiconductor processing stations. Automated transfer mechanisms often include a substrate support in which a substrate may have limited freedom of movement in at least one dimension. Such movement may result in the generation of particles and the misalignment of the substrate with respect to a processing system in which the substrate is placed. Significant substrate misalignment may reduce the number of devices that can be formed on a particular substrate or may cause the substrate to produce particles or even break inside the vacuum chamber. When a substrate breaks inside a vacuum chamber or when a substantial amount of particle contamination has accumulated inside the chamber, the chamber must be opened and exposed to ambient pressure; the chamber must be cleaned; and the chamber must be pumped back down to a sub-ambient pressure suitable for processing. In high vacuum processing applications, such a procedure may take up to twenty-four hours to complete, significantly delaying the time during which the system can be used to process substrates.
In one aspect, the invention features an apparatus for handling a substrate, comprising: a contact surface constructed to contact the substrate; a sensor constructed to detect contact between the substrate and the contact surface; and a clamping member having an extended condition wherein substrate movement relative to the contact surface is substantially restricted and a retracted condition wherein substrate movement relative to the contact surface is substantially free.
In another aspect, the invention features an apparatus for handling a substrate, comprising: a movable transfer arm having a support surface constructed to carry the substrate; a contact surface coupled to the transfer arm constructed to contact the substrate; and a vacuum sensor constructed to detect contact between the substrate and the contact surface.
The sensor may include a pressure transducer. The contact surface may define a channel opening. A housing defining a channel may be provided to couple the channel opening to a vacuum source. A controller may be provided for operating the clamping member between the extended condition and the retracted condition in response to signals received from the sensor. The contact surface may define a channel opening.
An edge restraint may be provided to contact a first peripheral edge portion of the substrate to limit substrate movement toward the edge restraint. In this embodiment, the extended condition of the clamping member may be characterized by the application of force by the clamping member against a second peripheral edge portion of the substrate urging the first peripheral edge portion of the substrate against the edge restraint. The extended condition of the clamping member may be further characterized by the application of force by the clamping member against the second peripheral edge portion of the substrate urging the substrate against the contact surface. The clamping member may comprise a pusher for contacting the second peripheral edge portion of the substrate, and a biasing member coupled to the pusher for biasing the pusher into the extended condition. The contact surface may be adapted to contact the bottom substrate surface, and the pusher may be adapted to contact only the top substrate surface along the second peripheral edge portion of the substrate.
In yet another aspect, the invention features a substrate handling apparatus comprising: a contact surface constructed to contact the substrate and to define a channel opening; a pusher constructed to contact the substrate; a biasing member having a first end coupled to the pusher and having a second end; and a housing defining a first channel wherein the pusher and the biasing member are disposed, with the second end of the biasing member being coupled to the housing and the pusher being free to move within the first housing channel, the housing further defining a second channel constructed to couple the channel opening to a vacuum source.
The housing may define a third channel through which the first housing channel is exposed to ambient pressure when the pusher extends out of the first housing channel beyond a fixed distance. An edge restraint may be provided for contacting a first peripheral edge portion of the substrate and thereby to limit substrate movement toward the edge restraint, wherein the biasing member biases the pusher against a second peripheral edge portion of the substrate urging the first peripheral edge portion of the substrate against the edge restraint, the third housing channel being closed by the pusher when the substrate is clamped between the edge restraint and the pusher. The housing may define a fourth channel through which the first housing channel is exposed to ambient pressure for determining when the pusher is unable to retract with the first housing channel beyond a fixed distance. The pusher may cut off the second channel from the vacuum source when the pusher is retracted within the first housing channel beyond a fixed distance.
In another aspect of the invention, the substrate handling apparatus comprises: a contact surface constructed to contact the substrate; an edge restraint adapted to contact the first peripheral edge portion of the substrate to limit substrate movement toward the edge restraint; and a clamping member coupled to the contact surface and biased to extend toward the second peripheral edge portion of the substrate thereby to urge the first peripheral edge potion of the substrate against the edge restraint, the clamping member being adapted to retract away from the second peripheral edge portion of the substrate when coupled to an energy source.
The clamping member may be adapted to retract away from the second peripheral edge portion of the substrate when coupled to a vacuum source. The clamping member may be adapted to retract away from the second peripheral edge portion of the substrate when coupled to an energy source independently of the position of the contact surface within a processing environment.
In yet another aspect of the invention, the substrate handling apparatus comprises: a movable transfer arm having a support surface constructed to carry the substrate; an edge restraint adapted to contact a first peripheral edge portion of the substrate to limit substrate movement toward the edge restraint; a contact surface constructed to contact the substrate and to define a channel opening; a pusher constructed to contact a second peripheral edge portion of the substrate; a biasing member having a first end coupled to the pusher and having a second end; and a housing defining a first channel wherein the pusher and the biasing member are disposed, with the second end of the biasing member being coupled to the housing and the pusher being free to move within the first housing channel, the housing further defining a second channel for coupling the channel opening to a vacuum source.
A sensor (e.g., a pressure transducer) may be provided for detecting contact between the substrate and the contact surface. A vacuum source may be coupled to the second housing channel. A flow restrictor may be coupled to the vacuum source, and a valve may be provided for selectively coupling the second housing channel to the vacuum source directly or through the flow restrictor.
In another aspect, the invention features a method of handling a substrate, comprising: providing a transfer arm having a contact surface constructed to contact the substrate and to define a channel opening, the channel opening being coupled to a first channel; coupling the first channel to a vacuum source; monitoring the pressure inside the first channel; and positioning the substrate on the transfer arm in contact with the contact surface.
A clamping member may be coupled to the contact surface and may have an extended condition wherein substrate movement relative to the contact surface is substantially restricted and a retracted condition wherein substrate movement relative to the contact surface is substantially free. Prior to positioning the substrate on the transfer arm, vacuum pressure may be applied to the first channel to place the clamping member in the retracted position. The vacuum applied to the first channel may be decreased in response to a decrease in the monitored first channel pressure upon the positioning of the substrate on the transfer arm, the decrease in applied vacuum being sufficient to place the clamping member in the extended condition. After the applied vacuum is decreased, the substrate may be re-positioned on the transfer arm when the monitored first channel pressure is higher than a predetermined maximum value.
The clamping member that is provided may comprise a second channel through which the first channel is exposed to ambient pressure when the clamping member extends beyond a fixed distance. After the applied vacuum is decreased, the substrate may be re-positioned on the transfer arm when the monitored first channel pressure is higher than a predetermined maximum value. After the applied vacuum is decreased, the vacuum applied to the first channel may be increased to place the clamping member in the retracted position.
The clamping member that is provided may comprise a second channel through which the first channel is exposed to ambient pressure when the clamping member extends beyond a threshold distance. After the applied vacuum is increased, the clamping member may be examined when the monitored first channel pressure is higher than a predetermined minimum value.
In another aspect, the invention features a method of handling a substrate, comprising: providing a transfer arm comprising a clamping member biased to extend toward the substrate and thereby restrain the substrate from moving relative to the transfer arm, the clamping member being adapted to retract away from the substrate when energized; energizing the clamping member sufficiently to retract the clamping member away from the substrate; and after energizing the clamping member, positioning the substrate on the transfer arm.
The clamping member may be energized by coupling the clamping member to a vacuum source. After the substrate is positioned on the transfer arm, the clamping member may be de-energized sufficiently to enable the clamping member to extend toward the substrate and thereby restrain the substrate from moving relative to the transfer arm.
Among the advantages of the invention are the following.
It has been realized that substrate movement relative to the transfer arm during substrate handling can generate particles and can result in substrate misalignment which prevents the substrate from being precisely and reliably positioned inside the processing stations. This problem has been addressed by providing a substrate handling apparatus that includes a clamping member having an extended condition for limiting substrate movement relative to the transfer arm and a retracted condition for freeing substrate movement relative to the transfer arm. The substrate handling apparatus further includes a sense mechanism for determining whether a substrate is properly positioned on the support arm and for triggering the mode of operation of the clamping member between extended and retracted conditions. The sense mechanism also provides information relating to the operating condition of the clamping member.
Other features and advantages will become apparent from the following description, including the drawings and claims.